The present invention relates to heat exchangers that are generally configured comprising a number of internal fluid or gas passages disposed within a surrounding body. In an example embodiment, the internal passages are designed to accommodate passage of a particular fluid or gas in need of cooling, and the body is configured to accommodate passage of a particular cooling fluid or gas used to reduce the temperature of the fluid or gas in the internal passages by heat transfer through the structure of the internal passages. A specific example of such a heat exchanger is one referred to as a shell and tube-type exchanger, which can be used in such applications as exhaust gas cooling for internal combustion engines.
Conventional shell and tube-type heat exchangers generally comprise a tube bundle made up of a plurality of individual tubes that are positioned within a surrounding shell. The shell is configured to both accommodate the tube bundle therein and to accommodate the passage of a cooling medium therein and along the tube bundle. Typically, the shell includes a coolant inlet and a coolant outlet to facilitate the passage of coolant therein, wherein the coolant inlet is positioned at one end of the shell, e.g., adjacent a hot-side inlet, and the coolant outlet is positioned at an opposite end of the shell, e.g., adjacent a hot side outlet.
A problem that is known to exist with such shell and tube-type heat exchangers is the unwanted boiling of the coolant within the exchanger during heat exchanger operation. For example, when such conventional heat exchangers are used to reduce the temperature of an incoming exhaust gas emitted from an internal combustion engine, e.g., when used in conjunction with an exhaust gas recirculation (EGR) system, a high heat flux can create an unwanted boiling of the coolant within the heat exchanger. Boiling of the coolant is undesired because it both reduces the cooling efficiency of heat exchanger, and because it produces a high-pressure condition within the heat exchanger that can damage and thereby reduce the heat exchanger service life.
Attempts that have been earlier made to reduce such unwanted boiling of the coolant has been to place baffles crosswise along an outside surface of the tubes to cause the coolant to pass within the heat exchanger along the tubes in a direction that was generally perpendicular to the otherwise flow path of the coolant, e.g., the use of the crosswise positioned baffles caused the coolant to flow in a serpentine flow path, thereby increasing the velocity of the coolant locally where the baffles induced a change of direction. This approach, however, both produced an unwanted pressure drop of the coolant moving through the heat exchanger, i.e., created an increased coolant pressure within the heat exchanger, and also created recirculation zones downstream of the baffles that resulted in unwanted coolant boiling just at a different location within the heat exchanger.
It is, therefore, desired that a heat exchanger be constructed in a manner that reduces and/or eliminates the potential for unwanted coolant boiling. It is further desired that such heat exchanger be constructed in a manner that does not otherwise impair the performance of the heat exchanger, e.g., that does not increase the pressure drop of the coolant moving through the heat exchanger.